A well known principle permits enclosure of hair in a polymeric matrix in the form of a strip and the manual removal of the strip by peeling to ensure hair extraction. For reasons of depilatory effectiveness, non aqueous polymeric compositions are generally preferred. Nevertheless, the requirements these depilatory polymeric compositions must meet are numerous and, for some, difficult to reconcile.
One requirement is to be able to bring and maintain the depilatory polymeric composition during the depilation process to a temperature adapted to provide the desired temperature in a fast and practical way.
Another important factor is the time for depilation duration, which time needs to be reduced because the depilation practice is tedious, and professionals as well as consumers wish to dedicate the least possible time to it.
Also, not only should the heating time be reduced, but the duration for which the polymeric depilatory composition remains usable during the depilation process should be the longest possible. Such duration of use is the interval during which the depilatory polymeric composition remains at a temperature acceptable for the skin, that is compatible with its homogeneous, easy and painless application, in a thin layer with a spatula or any appropriated applicator in order to be able to enclose the hair to be pulled. Currently, the duration of use, according to the here above-defined meaning, is in the order of 10 minutes for a 400 g pot of composition formulated according to the prior art.
Aesthetic criteria are important in that they can contribute to regular epilation practices; in addition, the epilatory polymeric compositions should also help to improve the overall experience of epilation by being able to adhere to short hair, therefore improving the epilation quality. The adherence of the composition to the hair has been incorporated into the formulation so as to obtain a very satisfactory and immediate high quality epilation, leaving only minimally visible, less numerous and shorter hair. Such improvement of the adherence also offers the possibility to proceed with a new epilation on short hair without having to wait for hair to regrow to a significant and unsightly length.
A depilatory polymeric composition must also meet other important requirements, regarding its rheology. Indeed, it is necessary to apply the depilatory polymeric composition in a thin layer, at a temperature acceptable for sensitive areas of the skin, without provoking the formation of threads susceptible to disrupt handling. Once the wax is frozen on the skin and the hair enclosed, it is essential that the strip produced be removed by hand, by peeling, in a single, fast movement. This entails that the laid strip should keep a certain deformability, suppleness and flexibility. On the other hand, these parameters must remain within values that do not affect negatively the cohesion of said strip and avoid stretching, making the removal of the strip difficult and risking the formation of composition deposits or residues adhering to the skin, which residues are always difficult and unpleasant to eliminate from the skin. In particular, for compositions forming strips on the skin, the composition rheology should be adapted to permit strip removal when the composition reaches a temperature at which the strip surface no longer adheres to the finger, i.e. a temperature at which the strip adheres minimally to the skin while keeping the required abilities for adhering to the hair.
Considering the intended use of the product, the depilatory polymeric composition may include at least dyes and/or perfumes for the sake of aesthetics. It is also possible to include solid particles or fibers, or ingredients intended notably to modify the presentation or aspect.
The prior art proposed depilatory waxes as described in French patent No. 2 751 872. However, such waxes only very partially met the requirements recited above, not permitting namely a homogeneous heating by a microwave heating oven.
Another European patent EP No. 299 816 proposed a rosin and elastomer-based depilatory composition of a disposable type. That patent, although not providing sufficient information, is characterized by the combination of an elastomeric or thermoplastic macromolecular compound, rosin and a plasticizer.
This invention proposes a depilatory polymeric composition that meets the numerous requirements described above, that is industrially feasible, comfortable to apply, and easy to use by consumers.